Woven jute and synthetic nettings have been used for the control of erosion for several years. The open nettings are too weak to provide sufficient soil stabilization, are difficult to handle, and have a tendency to tear during laying. The closed nettings are expensive, and, being nondegradable, tend to be lifted by grass growing under the netting, allowing wind to lift the netting from the ground. Eventually the netting must be removed by hand and effective control of erosion ceases.
Existing nettings have been employed or suggested for use in applications such as highway construction and maintenance, landscaping, and strip mine recovery. With the possible exception of certain landscaping applications, all such cases require a system needing little maintenance once the area covered by the netting is planted. It would be highly desirable to have a product which would both degrade enough to allow full development of vegetation and yet provide permanent erosion control.
U.S. Pat. No. 3,315,408 to Fisher is an example of a prior art woven fabric intended for the control of soil erosion. Although the patent suggests the utilization of different types of yarns, including biodegradable yarns and tubular or hollow core yarns containing agents or materials to be released (such as fertilizers, pesticides and weed killers), the woven fibrous material taught by this patent suffers from the deficiencies of woven materials, including limited flexibility and limitations upon the yarns which may be woven. Moreover, the fabrics taught do not possess sufficient versatility to provide a complete agricultural-horticultural system.
Other types of mulches or ground covers employing sheets of material, as contrasted with nettings, are disclosed, for example, in U.S. Pat. No. 3,205,619 to Henry, U.S. Pat. No. 3,302,323 to Popa, U.S. Pat. No. 3,467,142 to Boyle et al., U.S. Pat. No. 3,511,694 to Lippoldt et al., U.S. Pat. No. 3,427,194 to Lippoldt et al., and U.S. Pat. No. 3,516,196 to Lippoldt et al. The Henry, Popa, and Boyle et al. patents teach the utilization of such sheets for irrigation or fluid distribution. It has also been proposed to provide ground cover sheets with seeds, fungicides, fertilizers, insecticides, herbicides, and growth hormones, for example, to facilitate the planting and growth of grass or other plants. See, for example, U.S. Pat. No. 3,557,491 to Franklin et al. and U.S. Pat. No. 3,160,986 to Watson et al. However, it has not been possible heretofore to provide such elements and structures in a satisfactory open-mesh mulch, in particular a mulch having sufficient versatility and other basic characteristics to provide a complete agricultural-horticultural system.
U.S. Pat. No. 3,848,359--Seith et al.--discloses knitted fabric mulches for use in erosion control, landscaping and other agricultural uses. It is disclosed that the fabric may contain a degradable seed tape. This product has the disadvantage that it is complicated to form and further, the seed tape does not easily retain water, must be fastened to the fabric and is easily dislodged.
U.S. Pat. No. 4,429,001--Kolpan and UK Patent Application GB No. 2,113,731--Minto et al.--disclose the use of highly absorbent materials in a meltblown substrate to provide an absorbent layer. It is disclosed in the UK application that the absorbent material may be a clay, sponge or superabsorbent.
U.S. Pat. No. 4,100,324--Anderson et al.--discloses the melt-blown composite of a polymer fiber and cellulose fiber to form a nonwoven fabric.
There remains a need for an agricultural fabric that will be stable during the time of seeding, will degrade within a reasonable time, and further will provide protection and nourishment to the seed during germination and sprouting.